Religious communities

The major exception to the decline of spoken Yiddish can be found in Haredi communities all over the world. In some of the more closely-knit such communities Yiddish is spoken as a home and schooling language, especially in Hasidic communities such as Brooklyn's Borough Park, Williamsburg and Crown Heights, and in Monsey, Kiryas Joel, and New Square. (Over 88% of the population of Kiryas Joel is reported to speak Yiddish at home.) Yiddish is also widely spoken in the Antwerp Jewish community and in smaller Haredi communities such as the ones in London, Manchester and Montreal. Among most Haredim, Hebrew is generally reserved for prayer, while Yiddish is used for religious studies as well as a home and business language. In Israel, however, Haredim commonly speak Modern Hebrew, with the notable exception of many Hasidic communities. Nevertheless, the vast majority of Haredim who use Modern Hebrew also understand Yiddish. Many send their children to schools in which the primary language of instruction is Yiddish. Members of movements such as Satmar Hasidism, which views the commonplace use of Hebrew as a form of Zionism, use Yiddish almost exclusively.

Hundreds of thousands of young children have been, and are still, taught to translate the texts of the Genesis, Exodus, Leviticus, Numbers, and Deuteronomy into Yiddish. This process is called טײַטשן (taytshn) — "translating" . Most Ashkenazi yeshivas' highest level lectures in Talmud and Halakha are delivered in Yiddish by the rosh yeshivas as well as ethical talks of mussar. Hasidic rebbes generally use only Yiddish to converse with their followers and to deliver their various Torah talks, classes, and lectures. The linguistic style and vocabulary of Yiddish have influenced the manner in which many Orthodox Jews who attend yeshivas speak English. This usage is distinctive enough that it has been dubbed "Yeshivish".

While Hebrew remains the language of Jewish prayer, the Hasidim have mixed considerable Yiddish into their Hebrew, and are also responsible for a significant secondary religious literature written in Yiddish. For example, the tales about the Baal Shem Tov were written largely in Yiddish.